this old chestnut again:
Should we judge and punish a ten year old the same as we would an adult?
Haywain, if you feel you need to use cards to control 11yr olds and under, I would seriously look at your game management.
A stern word, public talking to and a nod to the coach is all that is needed at that for anything but the most serious foul play or Violent conduct.
Here in NZ, and I believe it's the same in UK, the Law deems a person 'not criminally responsible for their actions' until they are 13 yrs old, except in certain circumstances where there would be a whole lengthy court process to determine whetjer to try as an adult or not.
Why should it be any different once you are on the footie pitch playing 9v9, or 7v7 (when the LOTG state '11v11)